1. Field of the Invention
The present invention relates generally to methods of implanting an accommodating intraocular lens, and more specifically to implanting an accommodative intraocular lens wherein the accommodative state of the eye is controlled for a period of time before, during, and/or after a surgery.
2. Description of the Related Art
In the field of ophthalmic cataract surgery, wherein a defective natural lens is replaced with an artificial lens, there has been a development towards lenses and methods that inflict less surgical trauma and that provide accommodation (e.g., provide a focal point that is regulated by action of the ciliary muscle in the eye). For many years most of the IOLs were made of polymethylmethacrylate (PMMA), a material with good optical characteristics and compatibility with tissues in the eye. A disadvantage of PMMA, however, is that it is a very rigid material and a surgical incision must be made large enough, generally at least 5-6 mm, for the implantation of the lens. With improved devices for removal of the natural lens by phacoemulsification, requiring only a rather small incision, there was a need for lenses with foldable optics, as disclosed in the U.S. Pat. No. 4,573,998 (Mazzocco).
Even with the mentioned types of improved implantable IOLs, now available on the market, there is still a desire to obtain a lens which admits the use of an even smaller incision and behaves like the natural lens in the eye, i.e. will be accommodating with a focal point regulated by action of the ciliary muscle in the eye. In order to allow for a really small incision it would be necessary to form the lens inside the eye from a solution which is injected into the capsular bag or into a balloon placed inside the bag by means of a standard injection needle.
Another area of development in the field is the incorporation of accommodative IOLs, i.e., IOLs that at least partially restore the ability of the eye to focus both at near and distant objects. One approach for implanting an accommodating IOL is to form the IOL of a material that can be injected into and formed in the eye to provide a soft lens that is deformable in response to the ciliary muscle. Examples of IOLs formed from an injected solution of a silicone prepolymer, crosslinker and catalyst have already been suggested in U.S. Pat. Nos. 5,278,258 and 5,391,590 (Gerace et al), both of which are herein incorporated by reference. Other examples of injectable materials are disclosed in U.S. Pat. Nos. 4,542,542; 4,608,050 (Wright et al); and International patent application PCT/EP99/04715, all herein incorporated by reference.
In another approach, the accommodative IOL is formed prior to placement into the eye as disclosed, for example, in U.S. Pat. No. 6,443,985 (Woods), U.S. Pat. No. 6,846,326 (Zadno-Azizi et al.), U.S. Pat. No. 6,616,692 (Glick et al.), U.S. Pat. No. 6,488,708 (Sarfarazi), all herein incorporated by reference. Accommodative IOLs formed prior to placement in the eye are generally larger than monofocal or multifocal IOLs with equivalent optical power, thereby creating a greater need for foldable optical materials.
Accommodating IOLs, whether formed from a solution that is injected into the capsular bag or pre-formed for subsequent placement into the capsular bag, may be fabricated to have either an accommodative bias or a disaccommodative bias. When an accommodating IOL is fabricated with a disaccommodative bias, the IOL is configured to provide distant vision when the lens is in its natural or unstressed state. When the accommodating IOL is fabricated with an accommodative bias, the IOL is disposed to provide near or accommodated vision when the lens is in its natural or unstressed state. In both cases, it may be advantageous to maintain the eye in a predetermined state of accommodation during a post-operative time period over which cell growth onto at least portions of the IOL is used to secure the IOL to capsular bag or other parts of the eye.
U.S. Pat. No. 6,197,059 discloses an accommodating IOL having a generally disaccommodative bias. After implantation of the IL, the ciliary muscle is maintained in its relaxed state by the use of a cycloplegic to prevent dislocation of the IOL The cycloplegic may be initially introduced into the eye at the start of surgery to dilate the pupil and paralyze the ciliary muscle in its relaxed state. After surgery, cycloplegic drops are preferably introduced into the eye by the patient during a postoperative healing period while the anterior capsular remnant fuses to the posterior capsule of the bag. Once the cycloplegic effect wears off the ciliary muscle may again contract to move the optic anteriorly and provide near or accommodated vision.
However, this approach is ineffective for use with accommodating IOLs that are either injected into the eye or are otherwise implanted in an accommodative state. In such cases, the use of cycloplegic substances, as taught in the '059 patent are ineffective or even counterproductive, since such substances maintain the eye in a relaxed or disaccommodative state while the lens is in the accommodative state. Other approaches and methods are, therefore, needed that allow formation or placement of intraocular lenses having an accommodative bias in the eye.